Effort Values

As you may or may not know, EV's are a very important part of training any
pokemon. Just starting to be recognized by people other than breeders, EV
training helps pokemon become more adept in a certain area. They can be used
to give any pokemon the edge in a battle, or keep a pokemon in one. For
example, if you wanted to give a Raikou a boost in its Speed, you would
simply train it against pokemon that's speed stat is dominant. Another
example is if someone wanted to help Tyranitar land a bigger hit with
Crunch, which would have that person battle against pokemon that are more
dominant in Special Attack.

With that in mind, let's start with the basics. If you're wondering what
"EV" means, it simply means "Effort Value." It makes sense since you need to
put your effort into battling certain pokemon in order to get rewarded for
your efforts. Effort Values are hidden values, so you can't just look
somewhere in the pokemon's statistics to figure out how many Effort Values
you have already earned for a certain stat. Because of this limit,
calculating Effort Values requires you to record each pokemon, or at least
the EVs gained from the pokemon. If you want an easy way to do this, just
make a chart with six columns, label them according to the six different
stats, and place a tally for each point gained in the stat.

So now you're in a battle. Keep in mind that only battles where EXP counts
gives you an Effort Point, so no battling over a link cable or battle tower
to get Effort Points. Anyway, you have a Linoone, and you just defeated a
Zubat. Now, just like a pokemon's Base Values are set in stone (like Slaking
always having a base value of 160 in Attack), EVs are the same way. Anyone
who's ever trained a Zubat knows that the dominant stat is Speed, so if you
look at the Speed EV chart, you will see that Zubat gives 1 EV to Speed.
Most of the time, it's this easy. But sometimes you will find that a pokemon
gives EVs in an odd stat, like Charizard giving 3 EVs to Special Attack or
that a pokemon gives EVs to more than one stat, like Venusaur giving 2 EVs
to Special attack and 1 EV to Special Defense. Just watch out for those
things. If you can't find the EV, just use the pokedex to find it.

Now to explain how these work. Say the Linoone battled 4 Zubats and aquired
4 EVs in the pokemon's Speed EV. When it levels up, it will gain one more
point to its Speed stat than if it had battled three Zubats and one Geodude
(1 EV to Defense). This is because for every 4 Effort Points you get towards
a certain stat, you get one point more to the stat. If you wish for a less
technical explanation, let's call each Effort Value a Piece of Heart, like
in any Legend of Zelda game. If you get four Pieces of Heart, you get a
Heart Container. It's the same way with Effort Values. Of course, there has
to be a limit to this, seeing as if you battled 3,996 Zubats, you would have
a lot of time on your hands, and a Linoone with 999 located in its Speed

So, what are the limits? Well for starters, you can only gain 510 Effort
Values before they will stop being counted. 510 can be called our "Overall
Maximum", if you want a technical term. So this brings the Effort Points you
can gain to 126, once again as a maximum. But this is still a bit much to add
to any one stat, and it would make any Mewtwo have an absurd amount of
Special Attack still, or Blissey still having that huge potential to go over
700 Hit Points (not like you still can't get there.) So, to make it limited
still, there can only be a maximum of 255 Effort Points per stat, giving a
pokemon a potential 63 point increase in any stat.

So now, in terms of pokemon you have to battle, let's say you want that
Linoone to get its maximum speed. You would have to battle 255 Zubats to get
to the maximum speed value; EV training for any more Speed will become
useless if you choose to continue after 255. Now, I can imagine some of you
thinking, "Wow, I don't want to battle 255 pokemon to fill up on Speed EVs."
Well the good news is that you don't. The maximum points you can get for any
selected stat is 255, right? That's exactly what it is, a maximum. There are
a bunch of ways to lessen the EV training and make it less daunting.

Let's start with the simplest. Remember all those Proteins at the Energy
Guru and PokéMart in Veilstone that cost 9800 pokèdollars a piece? Those give 10 Effort Points to any
pokemon's attack stat. HP UP, Calcium, Iron, Carbos, and Zinc are similar of
course, giving 10 Effort Points to their corresponding stat. But once again,
this would make it too easy to EV train and will result in a limit. The
reason that those extra proteins that couldn't be used on your ultra-tough
Blaziken wouldn't work could be one of two reasons: 1. The stat is already
maxed out on EV points, or 2. You already used ten proteins on the Blaziken.
Since you can only use 10 vitamins on a single stat, this gives you 100
Effort Values possible to each stat this way. If you're one who is looking
for a rounded way of giving Effort Points to a pokemon and carries a lot of
money around, you could easily buy 10 Proteins, 10 Irons, 10 Calciums, 10
Zincs, 10 Carbos's, and a single HP UP and you will have already maxed out
your Effort Values this way

There's two more ways to make the whole EV training process go faster.
Remember the Macho Brace? That brace
will double Effort Points gained. Suddenly you earn 2 Effort Points for each
Zubat wearing the brace. Have you heard about the elusive Pokerus? That does
the exact same thing as the Macho brace. So now you have a Ninetales
carrying a Macho Brace with the Pokerus, and you just defeated a Spinda.
Since Spinda gives out 1 Effort Point to Special Attack, and you have both
the Pokerus and Macho brace, you get 4 Effort Points points to Special
Attack, which results in you gaining one more point to Special Attack on
your next level-up. Suddenly that 255 becomes 64 pokemon that you have to
battle to fill the Effort points up. Of course, the Pokerus doesn't appear
that easily, so good luck trying to get it.

However, that is not all. In Diamond & Pearl, there are a variety of Power items that will work similar to the Mach Brace, however they only work for one specific stat. Instead of just doubling the EVs gained in battle, the Power item will add 4 to it. So if you're battling a Gengar while your Pokémon holds the Power Lens that gives 3 Special Attack EVs, you will earn a massive 7 EVs which means almost 2 Points added, add to that the possibility of PokéRus, the possibilities get much easier. However these Power items do lower your Pokémon's speed. All of the items are obtainable for Battle Points in Battle Park so they're easy to get. Below is a list of which boosts which

Power Weight - Hit Points
Power Bracer - Attack
Power Belt - Defense
Power Anklet - Speed
Power Lens - Special Attack
Power Band - Special Defense

As for recommended places to train in R/S, try these:

HP - Whismur - Cave on Route 106
Attack - Carvanha - Route 119 (Super Rod)
Defense - Sandshrew/Skarmory - Route 113
Special Attack - Spinda - Route 113
Special Defense - Tentacool - Almost Anywhere you can surf
Speed - Zubat/Golbat - Cave of Origin

As for recommended places to train in D/P, try these:

HP - Shellos/Bidoof - Valley Windworks
Attack - Machoke/Bibarel - Route 211 East
Defense - Graveler/Onix - Iron Mountain
Special Attack - Gastly/Haunter - Old Chateau
Special Defense - Tentacool/Tentacruel - Route 220 or anywhere you surf
Speed - Staravia/Pikachu - Trophy Garden

If you want to know if your pokemon can earn more Effort Points, there's a
woman in Slateport's outdoor sales area (3rd Gen) or Sunyshore's Seal Market (4th Gen) that will give you a ribbon if you
have aquired 510 Effort Points, figuratively called the "Effort Ribbon."

So logically, it's best to start EV training immediately after you get the
pokemon. But of course, you can't get any Effort Points from those pokemon
like Carvanha with your newly hatched Mudkip (well you can but it'd be
hard). This is where the EXP. Share comes in. Any experience you get through
the EXP. Share is divided in half, so you'd think it would be the same for
Effort Values right? Actually, you get the same amount of Effort Values for
the battle as the pokemon fighting it did. So if your Mudkip had EXP. Share
attatched to it and your Blaziken defeated a Carvanha, both would get 1 EV
point, if they could. Sadly, you cannot manipulate the Macho Brace or
Pokerus to give Mudkip 4 EVs in place of 1 by using the EXP. Share. However,
if you were to send out Mudkip first with Macho Brace and Pokerus and
switch, it would gain the four Effort Points.

One last thing on EVs - Rare Candys. The so-thought dreaded item that
doesn't boost your stats as high as if you took the time to level up. They
usually accumulate in someone's box or are sold. Rare Candies, in reality,
do not take EVs into account when the stats increase. They're still there,
they just haven't been applied to the pokemon's stats yet. It's safe to use
them after the Effort Points are full.